A snake cannot live for any significant time after being cut in half.
Snakes, like all vertebrates, rely on a central nervous system to control vital functions such as breathing, circulation, and digestion. When a snake is cut in half, the spinal cord is severed, effectively separating the brain from the rest of the body. This results in immediate paralysis and loss of function in the lower half of the snake.
Furthermore, the snake's internal organs are exposed and vulnerable to infection and damage. The lack of blood flow to the lower half of the body leads to tissue death and necrosis.
In short, cutting a snake in half is a fatal injury that results in immediate and irreversible damage.